(a) Field of the Invention
The present invention relates to a method and a system for setting offset of a hydraulic pressure sensor which senses hydraulic operating pressure in a device (for an example, an engine clutch) using hydraulic pressure (oil pressure).
(b) Description of the Related Art
Many powertrain components such as transmissions and clutches utilize hydraulic pressure to operate and thus typically also utilize a sensor that is configured to sense hydraulic operating pressure. These components are used universally in all types of motor vehicles and are not limited to one particular vehicle type.
In particular, hybrid vehicles (i.e., vehicles that use two or more power sources, such as an electric motor and an engine. Referring to FIG. 1, the hybrid vehicle typically has an engine 10, a motor 20, and a transmission 40 arranged on a line. The hybrid vehicle 1 includes an ISG (Integrated Starter & Generator) 70 which is utilized to start the engine 10 or generate electricity from torque of the engine 10 and an engine clutch 30 which connects/disconnects power between the engine 10 and the motor 20.
The engine clutch 30 plays a substantially important role in the hybrid vehicles by appropriately combining the power from the engine 10 and the motor 20 in order to operate the hybrid vehicle. As such, FIG. 2 illustrates a conceptual view of a configuration of an example of the engine clutch 30.
Referring to FIG. 2, the engine clutch 30 includes: a friction material 36 movable by pressure (i.e., the hydraulic pressure) of a fluid (e.g., oil) 34 of which flow rate is controlled by operation of a hydraulic oil pump 50 (or a solenoid valve) and a return spring 32 which forces the friction material 36 to return to its original position when the hydraulic operating pressure is not being applied to the friction material 36. Typically in configurations like the one described above, the hydraulic oil pump 50 is controlled by a voltage and/or a current.
The hydraulic pressure (oil pressure) actually applied to the engine clutch 30 from the hydraulic oil pump 50 is sensed by the hydraulic pressure sensor 80. However, as shown in FIG. 3, an error can occur between an actual pressure sensed by the hydraulic pressure sensor 80 and an ideal pressure owing to the voltage applied to the hydraulic oil pump 50.
The error shown in FIG. 3 may include an offset error, a gain error, and/or a linearity error. As shown, the offset error typically causes an error in the hydraulic pressure sensed by the hydraulic pressure sensor 80 in a range of, for example, about +0.2 bar-−0.2 bar.
Because the pressure sensed by the hydraulic pressure sensor 80 plays an important role in control of the engine clutch 30, drivability of the vehicle may be adversely affected, unless the hydraulic pressure sensor 80 is appropriately calibrated, and particularly, the offset of the hydraulic pressure sensor 80 is appropriately corrected.
In the related art, the offset correction of the hydraulic pressure sensor executed after a predetermined period of time has passed. That is, in the related art, as a countermeasure to excess pressure—in the engine clutch 30, a processes is executed that determines that the pressure in the engine clutch 30 is dispersed when about five minutes of soaking time is passed the offset correction of the hydraulic pressure sensor is performed.
Accordingly, in the related art, when the soaking time is less than a predetermined period of time (e.g., five minutes), since the control is performed by sensing the hydraulic pressure of the engine clutch based on a previous offset, a control error is generated, which may deteriorate drivability.
A soaking time is defined as a period of time from ignition off to ignition on in this field of art.
Description of the Related Art is made to help understanding the background of the present invention and may include matters which are not the related art known to those skilled in this field of art.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.